This invention relates to hand tools, and more particularly, to ratchet wrenches of the type having a rectangularly shaped drive lug to which an accessory tool having a complementary receptacle can be attached.
Typically, a conventional ratchet wrench has an elongate handle attached to a head portion. The head portion contains a ratchet mechanism that causes the drive lug to rotate in a selected clockwise or counterclockwise direction when the handle is repeatedly swung back and forth through an arcuate path. In particular, when a fastener such as a bolt or screw is tightened or loosened, rotational force is applied to the fastener when the handle is swung arcuately in one direction, but the ratchet mechanism allows the wrench handle to be swung in the reverse direction without rotating the drive lug in the opposite direction and, hence, without applying force to the fastener.
Conventional ratchet wrenches perform adequately in many situations. However, when the space available around the fastener head restricts arcuate movement of the handle to a relatively small angle, a conventional ratchet wrench may be unusable, or at best, cumbersome and inconvenient to use. One proposed solution to this problem is a dual-mode ratchet wrench in which the drive lug can also be made to rotate when a sleeve-like section or portion of the handle is rotated about the longitudinal axis of the handle. In such arrangements, the sleeve-like section of the handle is coupled to the drive lug by means of a shaft and bevel gear system so that rotating or twisting the handle sleeve in one direction will cause the drive lug to rotate in the clockwise direction, while rotating the handle in the opposite direction will cause the drive lug to rotate counterclockwise. Examples of such prior art dual-mode wrenches are disclosed in U.S. Pat. No. 3,707,893 issued to Hofman, and U.S. Pat. No. 4,086,829 issued to Hudgins, both of which illustrate ratchet wrenches having a rotatable handle sleeve that can be rotated to rotate the drive lug to either tighten or loosen a bolt or screw-type fastener without swinging movement of the handle.
One drawback of the prior art dual-mode ratchet wrenches results from the use of a locking mechanism for engaging and disengaging the sleeve-like handle region with the bevel gear and other elements of the associated drive system. Such a mechanism requires the person using the wrench to use both hands to perform a change in the mode of wrench operation and may require that the wrench be removed from the workpiece in order to accomplish the change. In a limited space situation, removal and replacement of the wrench from a fastener is an inconvenience and results in wasted time. Attempts have been made to provide a dual-mode wrench in which the mode of wrench operation can be selected with one hand, as illustrated by the patent to Hudgins. Such prior art arrangements of this type incorporate a ball and groove detent mechanism that allows the wrench user to slide the sleeve-like handle region between an engaged and disengaged position with one hand. A detent-type retention system wherein the detent grooves are placed in the handle drive shaft, such as the arrangement shown in the patent to Hudgins, has the drawback of weakening the drive shaft and limiting the amount of torque that can be applied to a fastener.
Accordingly, it is an object of the present invention to provide a dual-mode ratchet wrench in which a change in the mode of operation can be accomplished by use of a single hand without removing the wrench from the workpiece. A further object is to provide a ratchet wrench of the above-described type wherein the wrench will not change mode of operation in an unwanted fashion. Another object is to provide a ratchet wrench of the above-described type wherein any mechanism used to permit a single hand change in the mode of operation of the wrench does not result in weakening any of the component parts of the wrench.